Circuit breaker



Dec. 18, 1934. H. D; DORFMAN 'l 1,985,023

CIRCUIT BREAKER Filed oct.- 2o, 1930 2 sheets-sheet 1 7ATTRNEY Dec. 18, 1934.

Filed Oct. 20, 1950 H. D. DORFMAN C IRCUIT BREAKER 2 Sheets-Sheet 2 ATT'ORNEY Patented Dec. I8, 1934 PATENT oFFlcE vBREAKEB.

Hiller D. Dorfman, Manseld, Ohio, assignor to Westinghouse Electric a Manufacturing Company, a corporation of lPennsylvania Application October 20, 1930, Serial No. 489,731

39 Claims. `(Cl. 21m-416)v My invention relates lto `circuit breakers and particularly to circuit breakers for controlling lighting and 'motor'circuits and which may be mounted in sheet-metal enclosures. 5 An object oi my invention is to provide a circuit breaker wherein the trip mechanism for causing opening movement is responsive to relatively low current values.

A further object of my invention is to provide a circuit breaker that, while capable of carrying relatively high current values, may be provided Y with interchangeable current-responsive releasing units adapted to release the breaker to open position at different current values, thus rendering a single circuit-breaker design suitable for a variety of diiIere'nt applications.

A further object of my invention is to provide a circuit breaker having the above-noted characteristics, wherein the current-responsive element,- having operating characteristics suitable for a given current range, may be calibrated for operation at any predetermined current value within that range. A further object of my invention is to provide a circuit breaker having a thermal element for releasing it that may have characteristics for operation within a given current range and be adapted to be heated by a number of diierent heating elements having diilerent current char- 30 acteristics, thus enabling the use of a thermal element of a standard design with elements having dierent heating characteristics for providing variations in the operating characteristics of the releasing unit.

A further object of my invention is to provide a circuit breaker having the above-noted char- Y acteristics wherein the apparatus mounted upon 'an insulating base, wherein the thermal element is mounted within an insulating block 40 that is 'detachably secured to the base and wherein the heating elements for the thermal elements areV mounted on insulating blocks detachably mounted upon the block containing the thermal elements.

These and other objects that will be made apparent throughout the further description of my invention are attained by means of the .apparatus hereinafter described and illustrated in the accompanying drawings, wherein:

Figure 1 is a top plan view of a circuit breaker embodying features of my invention, the heating elements being removed.

Fig. 2 is a view, partially in elevation and partially in vertical section, taken along the line II--II of Fig. 1. Y

Fig. 3 is an end view, partially in elevation and partially in vertical section, of the apparatus shown in Figs. 1 and 2.

Fig. 4 is a top plan view of a releasing unit, one of the heating elements being removed. 5

Fig. 5 is a transverse sectional view through the unit shown in Fig. 4, taken on the line V-V thereof, and

Fig. 6 is a transverse sectional view through the unit shown in Fig. 4, taken on the line l0 VI--VI thereof.

Referring to the drawings, the circuit breaker comprises an insulating base 'I upon which is mounted a sheet-metal frame structure 8 for supporting the circuit breaker unit which is l5 similar, in construction, to that minutely described in Patent No. 1,794,901, issued to Oliver S` Jennings on March 3, 1931 and assigned to the assignee of this application.

Briefly, the circuit-breaker unit comprises the 20 frame 8 upon which a cradle 9 is pivoted for rotation about the pivot pin 11. An operating arm 12, having a handle 13, is pivoted for rotation about the pivot pin 14, and apair of tension springs 15 are attached, at their outer ends, to 25 the arm 12 and, at their inner ends, to the knee pivot 16 of a pair of toggle links 17 and 18 which serve to operate a pivoted switch arm 19 that is mounted to oscillate about a pivot shaft 21 mounted on the frame 8, the link 17 being piv- 30 oted to the arm 19 by the pivot shaft 22, and the toggle link 18 being pivotally connected to the cradle 9 at the point 23 in the apex of a notch 24 of V-shape in the cradle.

The contact arm 19 carries a iiexible leaf 35 spring 25, upon the free end of which is mounted a movable contact 26 that is adapted to engage a stationary contact 27.

'I'he cradle 9 is releasably retained in theI closed position shown in Fig. 2 by means of a 40 latch 28 that will be hereinafter described. The circuit-breaker apparatus may be designated as of the tumbler type wherein an over-center spring serves to move the contact to open and r to closed positions. As shown in Fig. 2, the contact 26 is in open position and is moved to closed position with a snap action when the operating handle has been moved clockwise. a sufficient distance to move the outer ends of the springs 15 50 past a center line traversing the pivot shaft 16 and the point 23 referred to above. When this movement of the operating handle has been accomplished, the springs 15 will snap the lower pivot shaft 16 toward the right and straighten 55 j 26 into its closed position. i

When it is desired to move the switch to open lposition manually, the operating handle 13 is moved to the left or in a counter-clockwise direction, and, when the springs 15 again pass over the above-mentioned center line, the toggle will be broken with a snap action and cause the contact 26 to quickly separate from the contact 27.

In the event of an overload or a short-circuit condition, the latch 28 is released in a manner to be hereinafter described, and the springs 15, which are in an extended stressed condition when the circuit-breaker contact is closed, cause the cradle9 to turn, in a clock-wisedirection, to eiect breaking of the toggle and a consequent rapid separation of the contact 26 from the contact 27.

Since this form of circuit-breaker apparatus is completely described in the above-mentioned patent it is believed that no further explanation of the construction and operation of it is necessary for the purpose of this application, which is concerned more with the particular form of current-responsive releasing apparatus suitable for a multi-pole circuit breaker.

' However, it is to be understood that the present form of circuit breaker, as disclosed in Fig. l is of the three-pole type wherein the central pole comprises a circuit-breaker unit of the type above described, and wherein the outside poles comprise switch arms of the type shown in Fig. 2, without the trip and operating mechanism, since such mechanism is rendered unnecessary because the outside contact arms are connected to the -central contact arm by' means of an insulating cross bar 29. Insulating discs 30 are mounted upon the bar 29 between the contacts to increase the creepage path between the cony tacts.

Referring particularly to Figs. 4, and 6, the

4current-responsive tripping or releasing device comprises an insulating block 31 forming a base for the device and having two separate recesses 32 in which the current-respgnsive thermal tripping apparatus is mounted. This apparatus includes a metal cylinder 33 having an inwardly directed flange 34 to serve as a seat for the peripheral edge of a bimetal thermal disc 35 which is of such character that it becomes inverted when heated to a predetermined temperature and moves to the inverted position with a snap action. During the time within which the temperature of the disc is being raised, the metalV of the disc, between its center and its periphery, gradually assumes an S curve and, when the predetermined temperature is attained, the centerof the disc is moved axially to its inverted position with a snap action. When the disc cools below a predetermined temperature, the operation is reversed and the center of the disc snaps to its original position.

A diaphragm 36 is mounted in the cylinder 33 to support a heating coil 37 in spaced relation to the disc 35, the diaphragm being provided with elongated openings 38 for permitting the radiated heat of the4 heater to pass directly to the surface of the disc. The size and number of the openings 38 may be so varied as to permit more or less radiated heat to pass directly to the surface of the disc in order to vary the operating characteristics of `the releasing or tripping unit.

The heating coil 37 is mounted upon an insulating cover 39 and s connected thereto by means of terminals 41 which receive the ends 40 of the heating coil 37. The terminals 4l, as indicated in Fig. 4, are provided with flat sections 42 which are attached to the inner face of the insulating cover 39- by means of a hollow rivet 43, the flat portion being adapted to engage the outer faces of terminals 44 and 45, thereby forming a conductive path from the terminals 44 and 45 to the terminals 41 when the cover 39 is secured in operative position by means of screws 46 which extend through the hollow lvets 43 and are threaded into the threaded holes 47 in l the terminals 44 and 45.

By reference to Fig. 2, it will be seen that the heating coil 37 is connected in series with the contacts 26 and 27, the circuit being as follows: The live feed conductor 48 is attached to the terminal 49, and current passes from the terminal 49, through conductor strap 51, screw 52, conductor strap 53, screw 54, contact` 27, movable contact 26, flexible spring contact arm 25, flexible conductor 55, conductor strap 56, tubular rivet 57, screw 58, conductor Strap 44, terminal 41, heater coil 37, terminal 41, conductor strap 45, screw 59, tubular rivet 61, conductor strap 62, screw 63, conductor strap 64, screw 65, conductor strap-66 and terminal screw 67, to load conductor 68.

By reason of the construction described, heater elements having different operating characteristics may be placed in operative association with the bimetal disc 35 by substituting insulating covers 39 upon which are mounted heaters having diierent operating characteristics. Furthermore, a trip unit may be exchanged for another having heating elements of dierent characteristics by simply substituting insulating blocks 31 which, it will be understood, are attached to the insulating base 7 by means of the screws 5 8 and 59 and conductor straps 56 and 62 which are permanently attached to the base 7.

Additional flexibility of operation may be obtained by the vmedium of an adjusting screw ing the center of the disc to cause it to snap A to its inverted position a predetermined time after a predetermined overload hasv been imposed upon the circuit. The screw 69 is locked in position by a nut 71 that is threaded upon y the screw 69.

In order to protect the cover 39 from excessive heat generated in the coil 37, a mica disc 72 is attached to the underside of the cover by means of a rivet 73.

The latch mechanism for releasably retaining the cradle 9 of the circuit breaker in closed and operative position comprises the latch arm 28 that is pivotally mounted for oscillation about a pivot pin 74 carried by a bracket 75 secured in a recess 76 in the insulating block 3l. latch is provided with a notch or slot 77 through which the latch finger 78 of the cradle'9 extends when the cradle is moved to closed position. The latch 28 is releasably retained ln the latching position shown in Fig. 6 by a second latch 79 that 4is pivotally mounted upon abracket 81 which is mounted in a recess- 82 in the bottom face of the block 31. The latch 79 is free to rotate about a pivot pin 83 and is nor- The.

end

lposed extension 86 having a slot 87 therein for receiving the free end of the latch arm 28, the

[extension 86 being bent downwardly at its extremity ior permitting the end of the latch arm 28 to depress the latch 79 when the latch arm is Vmoved in a clockwise direction to latching` position by the linger 78 of the cradle 9. The spring 84 causes the latch 79 to rotate in a counter-clockwise direction when the free end of the latch arm 28 registers with the slot 87 in the extension 86.

The latch 79 is provided with two separate operating buttons 88 that may be adjustably positioned with respect to the latch and with respect to the bimetal disc 35, by means o! a screw 89 which is locked in'position by a threaded nut 91. An operating button 88 is centrally aligned with each of the bimetal discs 35 and, consequently, when either'disc is inverted, lin response to an overload or ,short-circuit condition, its respective button 88 is depressed with a snap movement to cause depression of the' latch 79 which, in turn, releases the latch arm 28. Since the cradle 9 is normally biased for movement in a clockwise direction, release ofthe free end of the latch arm 28 permits counter-clockwise movement of the latch to permit the latch finger 78 of the cradle 9 to clear the latch and snap to its open position.

The latch arm 28 is normally biased in a counter-clockwise direction by a coil spring 92 that is wound about'the pivot shaft 74 and has one end in engagement with the latch arm. The slot or notch 77 is so positioned and its length is sol proportioned that, when vthe cradle 9 is returned to its cled and operative position, the

finger 78l engages the lower end 93 of the notch and causes the latch arm 28 to be moved to its latched position, as shown in Fig. 6, it being understood that, when the latch ann 28 is in its latched position, the upper end 94 of the notch 77 engages the finger 78 and retains it in closed position.

Because the latch arm 28 is carried upon the insulating block 31 which supports the thermal discand the latch 79, the release mechanism constitutes a self-contained unit and may be adjusted or calibrated to operate to release the circuit breaker under any desired current condition independently of the circuit breaker device to which it is to berapplied. The relative positions of the flnger 78 with its cooperating latchvarm 28 is, in this case, no factor in the calibration, and may vary within manufacturing limits without in the least aecting the adjusted, set calibration of the release unit. Thereiore, a4 calibrated release unit may be associated orlassembled'with respect to a cradle 9 at diierent distances from the end-oi' the linger 78 of the cradle 9, without aiiecting the calibration.

Accordingly, a release or trip unit calibrated for a predetermined temperature and time may be substituted for one having a diilerent calibration, Without4 necessitating recalibration' after the unit is assembled with its respective circuit breakers.

1in-circuit breaker constructions where the circuit `breaker arm or its cradledirectly engaged the current responsive trip device and the calibration depended-upon the position of the latch with respect to its respective latch linger,

'calibration independent of the circuit breaker be changed in the iield by substituting release` units having different current ratings.

Asindicated in Figs. 2 and 3, the enclosure 7 is provided opposite each pair of contacts 26 and 27 with a metal gauze screen 95 for preventing the escape of arc flame rom the housing. It will be understood that the contacts may be surrounded by any lpreferred form of arc quenching devices for facilitating extinguishment of an arc drawn between the contacts.

Heretofore, circuit breakers have been releasably retained in closed and operative pom? tion by means of a bimetal strip which is anchored at one end and is heated by current passing therethrough. Current-responsive ther,

`:i1-ed heating eiect for operating a bimetal strip,

it has been necessary to reduce the cross sectional area of the bimetal strip to such an ex` tent that it is of insulcient mechanicalstrength to withstand repeatedoperations and to withstand shocks incident to shipment and installation, which shocks usually render the calibration' inaccurate.

Accordingly, I have developed a Aform of current-responsive thermal tripping device wherein relatively small currents soaffect the bimetal thermal disc that it is caused to operate positively and with great mechanical force. By making use of a bimetal disc, each increment of heat supplied to the disc by the heating element causes energy to be stored as potential energy` until suilcientexpansion of the material constituting the disc has caused the material' to assume an S curve, at which time, all of the .stored energy is instantly released to exert r`elaof standard construction may be made to oper@V ate, under different current conditions, throughout a relatively wide range, by simply substituting thermostat discs of desired size orby substituting a diierent heater for the thermal disc or by substituting a diierent diaphragm with the same heater and the same disc for obtaining a different characteristic of the releasing unit. Additional renement of operation may bel obtained by adjusting the position of the center of the thermal disc bymeans of the I adjusting screw. It is apparent, therefore, that. the circuit breaker is relatively flexible andcap-l able oi' use in a variety of iields of application.

While I have illustrated but one embodiment oi' my invention, it will be apparent to those skilled in the art that various changes, modiilcations, substitutions. additions and omissions may be made in the apparatus illustrated without departing from the spirit and scope of my invention. as set forth in the appended claims.

I claim as my invention:

1. The combination with a circuit breaker having a movable contact arm for controlling a circuit, means for biasing the arm toward open position and a latch releasable to permit movement oi the arm to open position, and means for normally moving the contact arm to open and closed positions while said latch is in engaged position, of a thermal release element for the latch comprising a thermal element energized by current in the circuit'controlled by the contact arm and having a portion mechanically inert until the element is heated to a predeter-` mined temperature, said element being movable with a snap action and exerting a force due to the energy imparted thereto from the circuit for releasing the latch when the element attains the said predetermined temperature.

2. The combination with a circuit breaker having a movable contact arm, means for biasing said contact arm toward open position, a latch releasable to permit movement of the arm to open position and means for normally moving the contact arm to open and closed positions, of a thermal release element for the latch comprising a thermal element energized by current in the circuit controlled by the contact arm and having a portion mechanically inert until the element is heated to a predetermined temperature and adapted to move with a snap action and exerting a force due to the energy imparted thereto from the circuit for releasing the latch when the element attains the said predetermined temperature, and saidlatch being releasable to cause the contact arm to move to open position irrespective of the position of said' means for normally moving the contact arm.

3. A circuit breaker comprising a movable contact arm, means for biasing the arm to open position, latch means for restraining said biasing means from moving the arm out of closed position, and a current-responsive release for the latch means comprising a bimetal invertible disc adapted to snap to inverted position and to operate the said latch to releasing position with a snap action when heated to a predetermined temperature, and a heater for the disc responsive.

to current in the circuit through the contact arm of the circuit breaker. o

4. A device for tripping a circuit breaker having a contact arm movable to open position uponrelease of a latch and comprising an invertible bimetal disc having a portion which remains inert until the temperature of the disc exceeds a predetermined amount and which moves with mounted on'a main base and having means i'or biasing it toward open position and having a releasable member for causing'movement oi' the circuit breaker to open position, of a self-con- -tained release unit for the circuit breaker having a separate base detachably mounted on said main base and comprising a current-responsive member adapted to be calibrated for releasing operation-in response to a predetermined current in the circuit controlled -by the circuit breaker, and a latch mounted on said separate base and releasably lengaging said releasable member on the main base and controlled by the current-responsive .memben 6. The combination with a circuit breaker having means for biasing it toward open position and having a releasable member for causing movement oi the circuit breaker to open position, of a self-contained detachable release unit for the circuit breaker comprising a current-responsive member adapted to be calibrated for releasing operation in response to a predetermined current in the circuit controlled by the circuit breaker, a latch actuated by the current-responsive member and a second latch releasably retained by the first latch for releasably engaging the said releasable member.

'1. The combination with a'. circuit breaker having a movable contact member for controlling a circuit and means for biasing said contact member toward open position, and a latch releasable to cause movement of the contact member to open position, oi' a current-responsive resettable release element for the latch comprising an element energized thermally-by current in the circuit through the contact member and having a portionmechanically inert until the element has been energized a predetermined amount and said element being movable with a snap action and exerting a torce due to the energy imparted thereto from the circuit ior releasing the latch when the element has been energized the said predetermined' amount.

8. The combination with a circuit breaker havy ing a movable member for controlling a circuit and means for biasing said member toward open position, and a latch releasable to cause movement o! the member to open position and movable at each operation various distances within a predetermined distance before causing the members release, of a detachable release unit having a movable contact member for control.

ling a circuit and means for biasing said contact member toward open position, and a latch releasable to cause movement of the member toward open position and movable a predetermined distance before causing the members to release. of a calibratable bimetal release element for the latch, responsive to stored energy vderived from the current in the circuit through said contact member, and having a Aportion that rapidly moves the latch a distance greater than the said predetermined distance` to release the said member, but which remains mechanically` inert until a predetermined energy has been stored in the said release element.

10. A multi-pole circuit breaker comprising a support, a plurality of movable contact arms mounted thereon and each controlling a difierent circuit, means for biasing the contact arms toward open position. a trip member biased 'to move to cause said contact arms to move to open position, and a detachable block mounted on the support and containing a latch for holding said trip member and upon the release of which the contact arms move to open position, and a separate, independently operable current-responsive device Afor one or more circuits for independently actuating the said latch.

11. In a circuit interrupter, a contact member movable to open and close the circuit, biasing means for moving said contact member to open position, a movable member in response to movement of which said biasing means moves said contact member to open position, and a main base on which said contact member, said biasing means and said movable member are mounted, and a trip unit including a separate base detachably secured to said main base and having mounted thereon means energized by the current through the circuit interrupter and a movable trip member controlled thereby for normally engaging and holding said movable member on the main base, said trip member remain- .ing in a fixed position until a predetermined current condition in the circuit through the circuit interrupter has been'reached and then moving immediately to cause movement of said movable member on the main base to open the circuit. f X

`12. In a circuitinterrupter, a plurality oi contact members movable to open and close the circuit, biasing means for moving said contact members to open position, a movable member biased to move and in response to movement of which saidbiasing means for said contact members moves said contact members to open position, and a main base on which said plurality ent circuit, biasing means for moving said contact members to open position, a biased movable arm in response to movement of which all of said plurality of contact members are moved to open position by said biasing means for moving said contact members, and a main base on which said plurality of contact members, said biasing meansand said movable arm are mounted, and

a trip unit including a separate base detachably mounted on said main base, and having mounted thereon a plurality of current responsive le- `men`ts connected in -the circuits through said movable contact members, a trip member actuable by any one of said current responsive elements and a latch movable upon actuation of "said trip member and having force tending to cause movement thereof applied thereto due to the bias of said movable arm on the main base.

14. In a circuit interrupter, a'plurality of movable contact members each controlling a diiferent circuit, biasing means for moving said contact members to open position, a movable arm innresponse to movement of which all of said plurality of contact members are moved to open position by said biasing means, and a main base V on which said plurality of contact members; said biasing means and said movable arm are mounted, and a trip unit including a separate base detachably mounted on said main base, and having mounted thereon a plurality of current responsive elements connected in the circuits through said movable contact members, a trip 5 member actuable by any one ot said current responsive elements and a latch controlled by said trip member and controlling said movable arm on the main base and said latch being held in xed position by said trip member until the l0 trip member has been actuated by one of said current responsive elements to a predetermined position and then being immediately released to cause opening of the contact members.

l5. In a circuit interrupter, a contact member 15 movable to open and close the circuit, biasing means for moving said contact member to open position, a movable member in response to movement of which said biasing means moves said contact member to open position, and a main 20 base on which said contact member, said biasing means and said movable member are mounted, and a trip unit including a separate base having thereon a pair of electrical terminals and a current responsive element to which said movable member on the main base is responsive, connected between said terminals, and fastening means detachably securing said trip unit base to said main base and said fastening means also electrically connecting at least some of said terminals in the Vcircuit through the circuit interrupter.

16. In a circuit interrupter, a contact member movable to open and close the circuit, biasing means for moving said contact member to open position, a movable member in response to movement of which said biasing means moves said contact member to open position, and a main base on which said contact member, said biasing means and said movable membereare 40 mounted and a trip unit including a separate base having mounted thereon. a trip member cooperating with said movable member on the main base and movable to cause the contact member to move to open position and a pair of electrical terminal members, fastening means detachably securing said trip unit 4base to said main base, said fastening means-also electrically connecting said electrical terminal members in the circuit through the circuit interrupter, and a current conducting element' mounted on a supporting member and having thereon a pair of electrical terminal members, and fastening means detachably securing said supporting member` on said trip unit base, the last said fastening means also electrically' connecting the terminals of said current conducting element to said terminal member on the trip unitl base.

17. In a multi-pole circuit interrupter, a plurality of movable contact members, an operating mechanism for normally actuating said contact members to open and closed positions, a main base on which said contact members and said operating mechanism are mounted and o5 conducting members securedto said base for y connecting said contact members in the circuit,

a trip unit having a separate base having mounted thereon a plurality of conducting currentresponsive elements, and fastening means detachably securing said separate trip unit basev to said main base, said fastening means also electrically connecting at least one end of each of said current responsive elements in circuit with said conducting members on the main base and in circuit with one of said movable contact members.

18. In a circuit interrupter, a movable contact member, biasing means for moving said contact member to open position, a pivoted member movable to cause said biasing means to move said contact member to open position, anda current responsive trip device i'or said movable member including a thermally responsive member responsive to the current through the circuitinterrupter, a latch member movable by said thermally responsive member, said latch being biased to oppose movement by said thermally responsive member and the amount oi movement thereof being determined by the amount of movement of said thermally responsive member, and a second member for causing movement of said movable member to move said contact member to open position, saidI second member being pivoted about an axis iixed relative to the pivot of said movable member and being held in iixed'position until the said latch has moved to a predetermined position and then moving immediately to released position.

19. In a multi-pole circuit interrupter, a movable contact member for each pole thereof, biasing means for moving said contact members to op'en position, a single member biased to move and cause said biasing means to move all of said movable contact members to open position, and a current responsive trip device for normallyholding said biased member includ- I 'ing a plurality of thermally responsive members each responsive to the current through one pole oi' the circuit interruptor, a trip bar extending across the plurality of thermally responsive members and being movable by any one thereof, said trip bar being biased in a direction opposite to the direction of movement of said thermally responsive members upon an increase in current, and the amount oi' movement of said trip bar being determined by the amount of movement of the one oi' said thermally responsive members which has moved the greatest distance, and a latch member normally engaging said biased member and being biased thereby to move to unlatched position for causing release of the biased member to move and cause all of said contact members to move to open position, said latch being held in xed position `until said trip bar has moved to a predetermined .ing means4 for moving 'said contact member to open position, a movable member in response to movement of which said biasing means moves base detachably secured to said main base, a.`

said contact member to open position, and a main base on which said oontact'member, vsaid biasing means` and said movable member are mounted, and atrip unit including a separate current responsive element, a trip member actuable in response to movement of said current responsive element and a latch member controlled by said trip member said latch member being movable to cause .actuation of said movthe contact members, and said movable member on the main base being movable to engage said trip unit and thereby cause resetting thereof.

21. In a circuit interrupter, a plurality of movable contact members each controlling a diiferent circuit,'biasing means for moving said contact members to open position, a movable arm in response to movement'oi which one or more of said plurality of contact members are moved to open position by said biasing means, and a main base of insulating material on which said plurality of contact members, said biasing means and said movable arm are mounted, and a trip unit including a separate base of insulating material detachably mounted on said main base, and having mounted thereon a plurality oi.' current responsive elements and a plurality `of conductors connected in series in the main circuits through said movable contact members for energizing said current responsive elements, said plurality of current responsive members on the separate base causingactuation of said movable `arm on the main base upon the occurrence of a predetermined current condition in the circuit through one of `said contact members.

22. In a circuit interrupter, a plurality of contact members movable to open and close the circuit, biasing means for moving said contact members to open position, a movable member in vresponse to movement oi which said lbiasing means moves said contact members to open position, and a main base on which said contact members, said biasing means and said movable member are mounted, and a trip unit including a separate base of insulating material detachably secured to said main base, said base of insulating material having mounted thereon a plurality of sectionsof conductor for connection in series with the main circuit through the contacts whereby said trip yunit is responsive to the current through the circuit interrupter, a pair oi' movable members mounted on said base of insulating material, the ilrst said movable member on the base oi' insulating material causing movement oi' said movable member on the main base substantially instantaneously upon movement of saidflrst movable member, and the instant when said movement takes place being determined by said second movable member on the base of insulating material having moved to a predetermined point.

23. In a circuit interrupter, a contact member movable to open and close the circuit, biasing means for moving said contact member to open position, a movable member in response to movement of which said biasing means'moves .said contact member to. open position, and a terrupten said fastening means also forming the only means fastening said trip unit base-to said main base.

24. In a multi-pole circuit interrupter, a plurality of movable contact members, biasing means for moving a plurality of said contact members to open position, a single movable memberin response to'movement of which a plurality of said contact members are moved to open position by said biasing means, a plurality of bimetallic trip elements each responsive to the current ilow through one of said contact members, a single trip bar extending across all of said bimetallic elements, said trip bar when mov to a predetermined point causing movemen of said movable member to open a plurality of said contact members, and said trip bar being movable by any one of said bimetallic elements, and means adjustable during the assembly and calibration of the circuit in-v terrupter for individually determining the amount oi movement of each of said bimetallic elements that is necessary to move said trip bar to said predetermined point independently of the adjustment of the other of said bimetallic elements. Y

2,5. In a. circuit interrupter, a plurality of contact members movable to open and close thecircuit, biasing means for moving said contact members to open position, a movable member in response tomovement of which said biasing means moves said contact members to open position, and a main base of insulating material on which said contact members, said biasing means -and said movable member are mounted, and a trip unit including a separate base of insulating material having'thereon a plurality of conducting means eachj having electrical terminals at4 the ends thereof, a plurality oi current responsive elements mounted on said separate base oi insulating material and each being responsive toV the current iiow between the terminals of one of said conducting means, and fastening means detachably connecting the terminals of said conducting means in series with the main circuit through the circuit interrupter.

26. In a circuit interrupter, a plurality of con- -tact membersmovable to open and close the circuit, biasing means for moving said contact members to open position, a movable member in response to movement ofwhich said biasing means moves said contact members to 'open position, and a main base of insulating material on which lsaid contact members, said biasing means and said movable member are mounted, and a trip unit including a separate base of insulating material having thereon a plurality of conducting means each having electrical terminals at the ends thereof, a plurality of current responsive elements mounted on said separate jb se of insulating material and each being res onsive to the current iiow between the terminals of one of said conducting means, and fastening means detachably connecting the terminals' of said conducting means in series with the main circuit through the circuit breaker,

an actuating element mounted on said separate base of insulating material for cooperating with said movable member on the main base to cause movement-thereof to trip the breaker and being separable from said movable member on `the main `base lto permit removal of the trip unit,

and means for retaining said actuating element in fixed position until one of said current responsive elements has moved to a predetermined point and then causing said actuating element to move immediately to cause movement of said movable memberv onl the main base to trip the breaker. Y

27. In a circuit interrupter, a movable cona tact member, biasing means for moving said contact .member to open position, a pivoted sponsive member responsive. to the current through the circuit interrupter, a latch member movable by said thermally responsive member, said latch being biased to oppose movement by said thermally responsive member and theA amount of movement thereof being determined bythe amount of movement of said thermally responsive member, and a second latch for normally holding and for releasing said pivoted releasable member to cause movement of said contact member to open position, said second latch being pivoted about an axis iixed relative to the pivot of said pivoted releasable member and being held in fixed position until the iirst latch has moved to a predetermined position and then moving immediately to released position.

28. In a multipole circuit interrupter, a main base, a pair of electrical terminal members for each pole mounted on said main base with the terminal members of each pair positioned opposite each other on opposite ends of the main base, a pair of separable contact members for each of a plurality of poles with each pair of contact members positioned between the pair of terminals for its pole and electrically connected to one of said terminals, a removable trip unit including a separate trip unit base having mounted l thereon a plurality yof conducting means removably positioned and electrically connected between said separable contacts and the terminals at one end of the main base, said separate tripunit base having mounted thereon a plurality of movable current responsive means each responsive to the current flow through one of said conducting means and said separate trip unit base having mounted thereon a movable trip bar extending across the conducting paths between said terminal members on opposite ends of the main base,'said trip bar being movable in response to movement of any one of said current responsive means to cause opening of the separable contacts.

29. In a multi-pole circuit interrupter, a main base, a pair of electrical terminal members for each pole mounted on said main base with the terminal members of each pair positioned opposite each other on opposite ends ofthe main base, a pair of separable contact members for cluding a member movable to cause opening of said separable contact, members, a removable trip unit including a separate trip unit base having mounted thereon a plurality of conducting means'removably positioned and electrically connected between said separable contacts and the terminals at one end of the main base, said separate trip unit base having mounted there on a plurality Xof movable current responsive means each responsive to the current ow through one of said conducting means, said separate trip unit base having mounted thereon a movable trip bar extending across the conducting paths between said terminal members on opposite ends of the main base, said trip bar being movable in response to movement of any one of said current responsive means, and an actuating elementmounted on said separate trip unit base for cooperating with said movable member on the main base to cause movement thereof, said actuating element being held in fixed position untilsaid. trip bar has been moved to a predetermined point and then moving immediately to cause movement of said movable member on the main base Aand opening of said separable contact members.

30. In a removable trip unit for a circuit breaker, a base of insulating material, a plurality of current .responsive means mounted on said base of insulating material, each of said current responsive means including a pair of current conducting terminal members and a bimetallic element responsive to the current ow between said terminal members, a pivoted trip bar mounted on said base, said trip bar extending across said plurality of bimetallic elements and being movable by any one thereof, and covering means of insulating material secured to said base and forming therewith enclosing means for said bimetallic elements, and said terminal members being on the outside of said enclosure. l

31. In a removable trip unit for a circuit breaker, a base of insulating material, a plurality of current responsive means mounted on said base of insulating material, each of said current responsive means including a snap-acting bimetallic disc-and heating means therefor, each of said heating means having a pair of electrical terminal members, a trip bar mounted on said base, said trip bar extending across said plural- Vity .of snap-acting bimetallic discs and being movable by any one thereof, and covering means of insulating material secured to said base and forming therewith enclosing means for said bimetallic-discs and said heating means, and said terminals for said heating means being on the outside of said enclosure.

means of insulating material secured to said base and `forming therewith enclosing means for said bimetallic elements, and said terminal members being on the outside of said enclosure, j

and an actuating element mounted on said base,

y said actuating element being held in xed position until said trip bar has been moved to a predetermined point and then being freed for immediate movement, and said actuating elementV being engageable fromtheoutside of said enclosure. f

33. In a-circuit interrupter, a contact member movable to open and close the circuit, an operating member for actuating said contact member to normally both lopen and close the circuit,

- biasing means for moving said contact member toppen position, a movable member in response to movement of which said biasing means moves Lsaid contact member to' open position, and a main basev on which said contact member, said -operatin'gomemben said biasing means and said movable member" are mounted, and a trip unit said main base and having mounted thereon means energized by the current through the circuit interrupter and a'movable trip member controlled thereby for normally engaging and holding said movable member on the main base, said trip member remaining in a xed position until a predetermined current condition in the circuit through the circuit interrupter has been reached and then moving immediately to trip' the circuit interrupter and cause movement 0i said movable member on the main base to open the circuit, and said movable member on the main base then being movable upon actuation of said operating member'on the main base to re-f latch with said trip member on the separate base, said movable member on the main base engaging said trip unit during said relatching movement and imparting movement thereto to return the trip device on the separate base to its normal condition.

34. In a circuit interrupter, a main base having mounted thereon a movable contact member, an operating member movable' for opening and closing said contact member under normal conditions, biasing means for moving said contact member to open position under abnormal conditions, a pivoted member releasable to,` cause said biasing means to move said contact member to open position, anda current responsive 'trip devicefor said releasable member including a separate base having' mounted thereon a thermally responsive member responsive to the cur.- rent through the circuit interrupter, a latch member movable by said thermally responsive l'member, said latch being biased to oppose move- 'ment by said thermally responsive member and the amount of movement thereof Abeing deter'- mined by the amount of movement of said thermally responsive member, and a second latch for normally holding and for releasing said pivoted releasable member on the main baseI to cause movement of said contact member to open position, said second latch being pivoted about an axis on said separate base xed relative to the pivot of said pivotedreleasable member on the main base when said separate base is mounted on said main base and said second latch being held in ilxedposition until the ilrst latch has moved to a predetermined vposition and then moving immediately to released position, and said operating member on the main base being operable to normally open and close said contact member-without release of said pivoted releasable member on the main base from said second latch on the separate base.

35. In a multi-pole circuit interrupter, a base -of insulating material having mounted thereon a movable contact vmember for each pole, biasing means for moving said contact members to open position, a pivoted member movable to cause said biasing means to move said contact members' to open position, and a current responsive trip device for said' movable member including a separate base of insulating material having a plurality of conducting means secured thereto and insulated from each other thereby, each of said conducting means having terminals at the. ends thereof for detachable connection in series in the. main circuit through the contactk members on the main base and fastening means' securing some of said terminals -to' the main base for attaching said separate U including a separatebasedetachably secured to responsive members each responsive to the rol maracas current through one o! said conducting means and the contact member of the circuit interrupter with which `it is in series, a latch member movable by said thermally responsive members, said latch being biased to oppose movement by said thermally responsive members and the 'amount of movement thereof being determined by the amount of movement of saidthermally responsive member which has moved the greatest amount, and a second member for causing movement of said movable member on the main base to move said contact members to open position, said second member being pivoted on said separate base about an axis fixed relative to the pivot of said movable member on the main base when said separate base is attached to the main base, and said second member being held in fixed position until the said latch has moved to a predetermined position and then moving immediately to released position.

`36. In a multi-pole circuit interrupter, a main base of insulating material, a pair of electrical terminalmembers for each pole mounted on said main base with the terminal members of each pair positioned opposite each other on opposite 4ends of the main base, a pair of separable contact members for each of a plurality of poles with each pair of contact members positioned between the pair of terminals for its pole and electrically connected to one of said terminals,

a member mounted on said main base and biased to move and cause opening of said separable contacts, a-removable trip unit including a separate trip unit base of insulating material havingmounted thereon a plurality of conducting means removably positioned and electrically connected between said separable contacts and the terminals at the other end of the main base. a latch member mounted on said separate trip unit base for normally engaging and holding saidmember on the main base against its bias, and said separate trip unit base having mounted thereon a plurality oi movable current responsive means each responsive to the current flow through one of said conducting means and said separate trip unit base having mounted thereon a-movable trip bar extending across the conducting paths between said terminal members on opposite ends of the main base, said trip bar being movable in response to movement of any one of said current responsive means to cause release of said'latch member and opening oi' the separable contacts.

37.'In a circuit interrupter, a movable contact member, biasing means for moving said contact member to open position, a pivoted member movable to cause said biasing means to move said contact member to open position, and a current responsive trip mechanism for said movable member including a thermally responsive member responsive to the current through -the circuit interrupter, a pivoted latch member movable by said thermally responsive member,

said pivoted latch member being biased to oppose movement by said thermally responsive member and the amount of movement thereof being determined by the amount of movement of said thermally responsive member, `and a second member biased to move and cause movement of saidV movable member to move' said contact member to open position, said second member being pivoted about an axis fixed relative to the pivot of said movable member and said second member being engaged by said pivoted latch member and being held thereby in fixed position against its bias until the said pivoted latch member has moved to a predetermined position and then being released to move immediately under action of its biasing means to released position.

38. In a multi-pole circuit interrupter, a movable contact member for each of a plurality of poles, biasing means for moving said contact members to open position, a pivoted member movable to cause said biasing means to move said contact members to open position, and a current responsive trip mechanism for said movable member including a plurality of thermally responsive members each responsive to the current through one of the contacts of the circuit interrupter, a latch member having a portion extending across said plurality of thermally responsive members and movable by any one of said thermally responsive members, said latch member being biased to oppose movement by said thermally responsive members and the amount of movement thereof being determined by the amount of movement of said thermally responsive member which has moved it the greatest amount, means between said thermally responsive members and the portion of said latch member extending thereacross, said means being adjustable .during the assembly and calibration of the circuit interrupter for individually determining the amount of movement of each of said thermally responsive members that is necessary to move said latch member to a predetermined position, said adjustment for each of said thermally responsive members being independent of the adjustment of the other of said thermally responsive members, and a second member for causing movement of said movable member to move said contact members to open position, said second member being pivoted about an axis fixed relative to the pivot of said movable member and being held in fixed position until the said latch member has moved to said predetermined position and then moving immediately to released position.`

39. In a multi-pole circuit interrupter, a plurality of movable contact members, biasing means for moving a plurality of said contact members to open position, a single movable member in response to movement of which a plurality of said contact members are moved to open position by said biasing means',` a plurality of bimetallic trip elements each responsive V to the current now through one of said contact members, a single trip bar extending across all of said bimetallic elements, said trip bar whenmoved to a predetermined point causing movement of said movable member to open a plurality of said contact members, and said trip bar being movable by any one Aof said bimetallic elements, and means adjustable during the assembly and calibration of the circuit interrupter for individually determining the amwount of movement of each of said bimetallic elements that is necessary to move said trip bar,y to said predetermined point, said means including an insulatingbutton mounted between each of said bimetallicelements and said trip bar and said 

